3D LUT shader for colour correction about vkbasalt HOT 13 CLOSED

Thanks. Just figured out it was the "Tone Curve" setting in DisplayCAL causing the problem, for the record (use Rec. 1886 instead of Gamma 2.2, and manually choose a 2.2 gamma after that).

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So by 3D LUT what file format do you mean? Some sort of .png or these .cube that image manipulation software uses? On an other note that shader you linked uses 2d images internally which seems weird for a 3d LUT.

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@DadSchoorse PNG files, yes.

I don't have a deep understanding of how it works, but I believe you use several 2D textures but treat them as 3D (presumably R, G, B + Alpha):

See this link:
https://threejsfundamentals.org/threejs/lessons/threejs-post-processing-3dlut.html

WebGL1 doesn't support 3D textures so we'll use 4x2 2D texture and treat it as a 3D texture inside a custom shader where each slice of the cube is spread out horizontally across the texture.

And another example implementation, this time as a slang shader in Retroarch: https://github.com/libretro/slang-shaders/blob/master/crt/shaders/guest/lut/lut.slang

You can also see some example LUTs in that repo, e.g. one that simulates the colours of a .

And this port from reshade to retroarch. This one looks slightly simpler and doesn't have unrelated options.

It would be nice to support several different sizes for the LUT png (DisplayCAL can export to 16x16x16, 32x32x32, and 64x64x64 colours), although 64x64x64 would be enough to begin with.

Thanks

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I have implemented a 3D LUT shader in the wip-lut branch. It supports PNG like that one and .CUBE files. To use it, set effects = lut and lutFile = /path/to/lut/without/spaces in the config.
Here's a build:
vkBasalt.tar.gz
Testing would be appreciated.

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Thanks! Just tested, and it works as expected so far (with native Vulkan and D9VK/DXVK). I've only tested DisplayCAL generated LUTs (which are the most important for me) so I'll try and test some others.

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CUBE LUTs also look to be working well.

The only issue I've had so far was one particular .png LUT causing a strong yellow tint with Rise of the Tomb Raider (and only that particular game). There's a decent chance that the LUT itself is the problem, although I've been using the LUT with ReShade for a while and it's the first time I've had an issue with it. A new CUBE LUT with similar settings doesn't have the issue, for the record.

I'll try and figure out if it's the LUT at fault, rather than your code.

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Can you give me the yellow LUT?

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@DadSchoorse Sure.

lut-dcip3

It's not hugely noticeable but it should be visible when comparing screenshots. Here's a comparison to show what I mean:

No LUT

PNG LUT

Cube LUT

These are intended to be run on a wide gamut monitor, but the yellow tint should be noticeable with standard gamut monitors as well. I used different gamma settings on the Cube LUT, so ignore the brightness difference.

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It does not seem to cause a yellow tint in my testing:

This is without the LUT:

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I think it's just game specific. I also tested generating a CUBE lut with the same settings as the older PNG and it does exhibit the same problem. It might be those particular settings cause problems in only certain games.

I can most likely just work around it on my end by choosing different settings.

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Okay then I am going to merge the branch and close this issue.

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Thanks. Just figured out it was the "Tone Curve" setting in DisplayCAL causing the problem, for the record (use Rec. 1886 instead of Gamma 2.2, and manually choose a 2.2 gamma after that).

Sorry for reviving this old topic but i wanted to ask you if with "use Rec. 1886 instead of Gamma 2.2" you mean to do the calibration with this setting and then changing it to Gamma 2.2 when creating the 3D LUT?

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@HexHyte Sorry I missed your comment. I wish I'd made more detailed notes, because I'm honestly not sure.
The default setting would be to calibrate with a "Gamma 2.2" tone curve, then map that to a 3D LUT with source colourspace "Rec709" and tone curve "Rec 1886". I'll add that I haven't seen any obvious issues with recent LUTs I've made with close to the default settings, but I haven't looked at Rise of the Tomb Raider recently.

As a side note, the flatpak version as of today doesn't include all available source colourspaces (such as Rec 709 which you want for standard sRGB content). A workaround is to extract the binaries of the latest argyllcms somewhere, and load them with displaycal. See here

EDIT: I may have meant in the 3D LUT tab to use Rec 1886 tone curve but change the gamma from 2.4 to 2.2 (with advanced options enabled). Or you could try gamma 2.2 both in the calibration and 3D LUT which would probably be fine for most content.

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